Characterization of Hot‐Pressed Cement Pastes

Abstract

Very‐high‐strength cement pastes (compressive strengths ∼100,000 psi) were prepared using hot‐pressing techniques at temperatures up to 250°C. The results of characterization studies summarized include X‐ray diffraction, DTA, ir spectra, and microstructural investigations. Much less Ca(OH) 2 is formed than in normally hydrated pastes. Some well‐ crystallized hydroxyl‐containing hydrates, C 5 S 2 H, C 3 SH 1.5 , C 3 AH 6 , and C 4 A 3 H 3 , as well as poorly crystalline CSH, are formed. The structure of the CSH, as revealed by ir absorption studies, does not appear to be very different from that in low‐ temperature hydrated cement pastes. Microstructures are extremely dense and, in some cases, the sulfate‐containing phase concentrates along original grain boundaries.